The subject matter disclosed herein relates to rotorcraft flight parameter estimation and, more particularly, to rotorcraft airspeed estimation using a horizontal stabilizer input.
Information reflective of airspeed of an aircraft, such as a helicopter, is commonly obtained using pitot-static tubes that are typically mounted near the front of the helicopter. Airspeed is a key regime recognition parameter that is used to schedule control gains and to operate trim devices to guarantee high levels of handling qualities and stability margins. These control gains and trim devices, such as a horizontal stabilizer, are scheduled using a blended airspeed variable that is a combination of ground speed and airspeed depending on the reliability of each measurement. For UH-60 helicopters, as an example, at airspeeds above about 30 knots, the pitot-static tubes are not in the downwash of the rotor system and therefore the airspeed measurement is held to be relatively highly accurate for that flight regime.
Depending on the criticality of airspeed for flight controls and survivability of the aircraft, sensor failure can be an issue for current aircraft. Sensor failure can occur, for example, when the pitot-static tubes are clogged with ice or dust.